1. Field of the Invention
The invention relates to a process for the production of concrete paving stones having, in the region of upright side faces, web-like distance pieces, the height of which is smaller than the height of the rest of the paving stone, the paving stones being produced in a concrete mold, which is preferably provided with a plurality of individual molds with adjacent recesses, by filling the fresh concrete into the concrete mold which is open at the top, and subsequently compacting the concrete. The invention furthermore relates to an apparatus for carrying out this process, and to a concrete paving stone which is produced by means of the foregoing process and apparatus.
Concrete paving stones having, on their side faces, integral distance pieces, which are thus also made of concrete, are gaining increasingly in importance for making so-called lawn pavings.
To this end, the distance pieces have a dimension (thickness) which creates relatively wide gaps within the ready laid paved floor. These gaps are filled with soil and allow the growth of plants, especially lawn, within the gaps.
2. Description of the Related Art
The industrial production of such concrete paving stones creates problems because of the smaller height of the distance pieces compared to the paving stone itself. The concrete molds which were mostly used in practice hitherto are comprised of a molding box with die cavities having recesses for forming the distance pieces which are arranged in separating walls of the molding box, and which extend over the entire height thereof. The fresh concrete is filled into the die cavities and the recesses from the top. For compacting and shaping the concrete paving stones, a pressure device is lowered onto the molding box from above. Individual pressure rams enter into the die cavities with die plates. Projections arranged on the sides of the die plates are assigned to the recesses and compact the concrete within the recesses. The projections have a greater overall height than the die plate itself and project downwardly therefrom. As a result, the smaller height of the distance pieces is formed during the compaction of the concrete.
Since the recesses are filled with fresh concrete over their entire height, a higher compaction is created inside the recesses than in the region of the die cavities. This may result in a lower compaction of the concrete blocks themselves. Moreover, as a result of the higher compaction in the region of the recesses, residual concrete is taken along when moving the molding die upwards, specifically also in a region of the top side of the concrete paving stone adjoining the distance pieces. As a result, a relatively large number of rejects is produced.